The invention relates generally to component packaging processing and more particularly to multiple process sequences to protect sensitive embedded solid state components during advanced packaging process operations and/or second level assembly processing.
Active and passive solid state components often have thin bonding metals or alternate materials applied to them for subsequent bonding or process insertion steps for next level assembly processing. These metals or coating can be sensitive to processing treatments that could poison or otherwise have a negative impact on their performance. Examples of some coatings on the components include, without limitation, materials such as thin metals. Exemplary thin metals include Au, Ag, Pd, Ni, Sn, Pb, and so on. Other coatings could include organic coating such as an organic solderability preservative (OSP) or other encapsulant materials.
Keeping the foregoing discussion in mind, the dies used in certain power overlay (POL) modules have backside metallization, most of which have upper layers of nickel and silver. During the POL module processing, the silver gets oxidized (poisoned). This oxidation undesirably prevents the solder from wetting the nickel/silver during second level assembly, and has resulted in additional processing and rework steps to make the associated POL devices solderable and usable.
The foregoing component packaging problems have historically been addressed simply by protecting the backside of dies with blue membrane material or sealing Kapton to the backside of the dies to be protected. Another technique that has been employed is the use of backed carriers. These options protect the backs of the die(s) from chemical etching or attack. These options do not however protect the silver from oxidizing at the high temperatures used in the processing of silver backed dies.
Another technique for addressing the foregoing component packaging problems has been deposition of a Ti/Ni/Au layer over the die before starting the POL processing. This technique is undesirable due to the high cost and handling issues associated with very thin dies used in the POL process.
In view of the above, it would be both advantageous and beneficial to provide a robust backside metallization that is compatible with advanced processing and the POL process. It would be further beneficial if the robust backside metallization processing steps were compatible with existing manufacturing processing and equipment and resulted in a decrease in manual operations.